Let's look at the origins: the biquadrate is considered a subspecies of frame antennas, which first of all belong to the genus of zigzags. The first antenna Kharchenko offered Kharchenko K.P.In 1961, for catching TV shows. It is known for certain: at a frequency of 14 MHz, putting a biquadrate in a meadow, an ardent enthusiast managed to get America. Not a bad result. We believe the case affects refraction, plus diffraction beats the Earth. HF range, and below, are used due to the ability of waves to refract, to go around obstacles, it is possible to establish communication at a great distance. Let's take it in order. Let's take a closer look at how the Kharchenko antenna is made by hand.
Antenna Kharchenko, the "eight", which today is caught by WiFi, cellular 3G.For outdoor installation, protect the product with a plastic case.
Communication and antennas Kharchenko
Later it will become obvious: the device of the original antenna Kharchenko, to put it mildly, differs from that observed in the network today. Not that they loved, as Mayakovsky used to say, to delve into the prehistoric r. ... but the basics of the theory must be studied in order to avoid mistakes, to know the peculiarities of the construction work. We are going to tell you how to make a Harchenko antenna yourself. The author of the monograph avoids giving instructions on the choice of the thickness of the wires, says: a reduction in diameter adversely affects the range. Kharchenko’s homemade antenna is capable of covering 470–900 MHz digital television spectrum. Characteristics of the device are delightful, coordination is not of great complexity. We will tell you how to make the Kharchenko antenna, avoiding delving into the theory. We recommend to the miners to review the original thematic edition of the author.
The length of the 14 MHz biquadrate wire is approximately 21 meters. So much cable-vole will need to make a simple device. The device is powered by a television coaxial wire( characteristic impedance of 75 ohms).Eyewitnesses are sure: tuning of Kharchenko’s antenna is not requiredThe authors are inclined to consider the latter as a small( gigantic) exaggeration. Think about it! You can plow the natural landscape by putting your back on two coils of wire:
- coil of coax cable television.
Then expand the antenna, the range of which is simply amazing. Polarization depends on which side of the eight to rotate. Let us arrange reluctantly how the tsiferki icon is spelled in arithmetic textbooks - let’s take television, fill it up sideways, forming infinity - radio broadcasting will begin to catch itself. Since the vole bends well, unbends back: I don’t like one channel, we can quickly orient the antenna to another. The problem is hateful: an extra wire that is unnecessary for useful needs will have to either be cut off or reeled off with a coil, placed in such a way as to not interfere with reception. And this is not such a trivial task, as it seems to the first one to meet:
- you put it horizontally - it will begin to catch television;
- stretch to the ground - the intermediate wire will begin to accept vertical polarization;
- you will hang on a bough - vertical polarization will be caught.
No matter how sideways you turn the extra cable, no matter how you put it, interference is guaranteed. Check the azimuths, try to find the angle of arrival of the broadcast. If the direction is the only one, we wind a long stick with wire, place it perpendicular to the line of sight at the station, minimizing the parasitic effect to zero.
Antenna Design Kharchenko
Probably used to see the same thing in the figures. Here's how to design the Kharchenko antenna( the VashTechnik portal keeps up):
- It is necessary to find out the frequency of the wave, the polarization. Antenna Kharchenko friendly linear.
- The copper antenna is made up of two squares. Both are on the corners, one in contact. For horizontal polarization, the eight stands upright;vertical - lies on its side.
- The side of the square is the formula: wavelength divided by four.
- One can imagine the construction if one imagines an oval that is stretched in the center across the larger side. The sides do not touch, although they are close to each other.
- The power cable is routed to the side draw points. It is necessary to block one direction of the diagram - a flat copper screen is placed at a distance of 0.175 of the working wavelength, planted on the braid of the power cable. The reflector is made of a metal plate. In the old days, textolite boards coated with copper were used.
Completed brief Kharchenko antenna design. Details are overgrown with problems: the task is to strengthen the emitter. For the communication range - wire stretch marks;Television - often used a wood frame, studded with crossbars( resembling a cross), in the microwave range, the modem owners propped up the radiator with a pair of plastic racks penetrating the screen. What thinks about the concepts of construction Kharchenko. Submissive slaves of the portal VashTehnik bother to get a book of authorship of the engineer, the text describes the invention, the mountain of interesting is written:
- Firstly, when the side of the square is a quarter of the wavelength, we can see the lower frequency of the range. The author did not comprehend the top, but we can calculate indirectly, using skillfully considerations( the figure describing the construction below).Shown: the frame consists of three conductors( more than one).Individual sizes of cuts, the height of the average square is equal to 0.28 wavelength of the lower frequency. We see nothing difficult to multiply the reference value by cos 45, to find out: the size of the side is 0.198 wavelength. According to Kharchenko, at the announced frequency, the side of the frame is a quarter of the wavelength. We conclude: it affects a larger square, the smaller side is approximately 0.14 wavelength. Continuing the analogy, we divide the great into the small, we get: the range factor is 1.8.Kharchenko K.P.He casually mentions: the radiation pattern is maintained at the ratio of the maximum and minimum frequency of 2 - 2.5.The book cites a picture of a catch antenna for broadcasting in the two bands 50-100 and 174-230 MHz. It is possible, going along the beaten track, to present the possibilities given by the product in terms of channel overlap. That is why in the manufacture of the Kharchenko antenna for WiFi according to the scheme indicated above, it should be based on the lowest frequency used. Otherwise, part of the signal will go beyond the operating limit of the antenna. The fact is directly ignored, the conclusion follows from the author's presentation of the material Kharchenko. Although the engineer here says that the geometrical errors are not important, the working antenna range is very wide.
- Mentioned the wound: there are three frames, the distance between the extremes( along the perpendicular cross section of the wires) is 0.033 of the maximum wavelength( minimum frequency).We believe that readers themselves will calculate the dimensions( and, perhaps, they will find that they made a mistake a little higher), but this is not the point. These three frames are assembled on the mast, have a radiation pattern, which also has a vertical component. Increasing the frequency reduces the parasitic effect. It was recommended to read the original: it turns out that when producing the Kharchenko antenna at a fixed frequency, the wave should be in the upper part of the range. The fact is not described anywhere, the author claims that throughout the whole spectrum the level of the parasitic vertical component is 26 dB lower than useful.
- Add to this, in the upper part of the range, a distribution of currents is formed, at which Kharchenko's antenna will avoid matching, while a transformer will be needed in the other segment. The device can be made from a length of 100-ohm coaxial cable length. .. and here the author suffered. The text contains the figure of 0.052 of the maximum wavelength, in the figure - 0.139 of that length. Try this and that way. .. It is known that if RK 1 is used for power supply, the transformer is made of RK 3. And vice versa, when powering RK 3, the transformer is made of RK 1. In our opinion, the material is described unconstructively. .. In the first case, we remove the insulation and braid of RK 1on the segment of the transformer length, we replace the sounded farm RK 3, from which the central core is pulled out. In the second case, on the contrary, we extract the core of the power cable RK 3 for the transformer length, replace the residential cable RK 1.
The geometrical dimensions indicated, we list together:
- The height of the square standing on the angle is 0.28 of the maximum wavelength, along the middle contour of three.
- The distance between the outermost frames across the wire direction is 0.033 of the maximum wavelength.
- The length of the matching line with an impedance of 100 Ohms - 0.052 or 0.139 maximum wavelength.
What else I would like to notice by the original design. .. In order not to disturb the Kharchenko's antenna field, the power cable comes from below, winds along one side of the frame, enters the center. Does not go lived on the mast! Modern designs imply the presence of the screen. Therefore, the wire comes from somewhere behind, breaks through the copper screen, is connected in the right place to the eight. It is not necessary, by the way, that the antenna consists of squares. The device characteristics do not depend much on the angle at the vertex. The height of the eight( standing upright) must be maintained. Therefore, if the angle changes from 90 to 120 degrees, the sides are extended. In proportion. You can count specific values.
Now readers know how to make a Kharchenko antenna with their own hands. And one more thing. It was possible to see, surfing the network, constructions where the emitter was bent around the screen. Thus, the main lobe of the radiation pattern is supposedly expanded. In practice, in this case it is easier to use the patch. Here the site can just be sent in different directions.